The present invention relates to a heater and, more particularly, to a rod-shaped heater or a plate-like heater which uses a carbon wire heating element with a quartz glass member sealed therein.
In various heat treatment atmosphere in oxidation, diffusion or chemical vapor deposition (CVD) treatments conducted in the semiconductor manufacturing process, a strict temperature control is required.
Further, in the semiconductor manufacturing process, a strict temperature control is also required for a wet etching agent, a grinding agent or the like as used in other cleaning or grinding processes.
For this temperature control in such processes, a rod-shaped heater or a plate-like heater is widely used.
As an example of such heaters, there has been proposed a heater which has a heating element made of tungsten material, the outside of said heating element being covered by a quartz glass tube.
Since such a rod-shaped heater or a plate-like heater is directly dipped in a storage tank which stores a wet etching agent, a grinding agent or the like, there is a technical problem left unsolved that once the quartz glass tube covering the heating element should break, said wet etching agent or said grinding agent will be subjected to metallic contamination, leading to contamination of the wafers which are going to be ground or cleaned.
Even if said quartz glass tube is not broken, there still is a gradual metallic contamination of the wet etching agent or the grinding agent by way of the quartz glass heater from said heating element.
The inventors have already proposed in Japanese Patent Application No. 10-254513 a heater for semiconductor manufacturing which employs a carbon wire heating element that may be used advantageously as compared to said metallic heating element.
Said carbon wire heating element is manufactured by binding very fine carbon filaments into a carbon fiber bundle and weaving a plurality of such carbon fiber bundles.
Said carbon wire heating element have a small heat capacity as to provide an excellent temperature rising and decreasing characteristics as compared to the conventional metallic heating element and an excellent heat resistance in a non-oxidizing atmosphere.
Further, since a plurality of fine carbon filaments are woven into carbon fiber bundles, the thus manufactured carbon wire heating element has advantages such as more flexibility than a heating element of a solid carbon material and it is easy to work the material into various structure or shapes.
The present invention is made to solve the above mentioned technical problem which the rod-shaped heater or a plate-like heater conventionally faces by use of said carbon wire heating element and its objective is to provide a heater suited to raise the temperature of the wet etching agent, the grinding agent or the like by dipping directly into the storage tank.
Particularly, the present invention has it an objective to provide a heater which can prevent the metallic contamination of the wet etching agent, the grinding agent or the like, and which has a mechanical strength against any breakage in the event of direct dipping into the storage tank of the wet etching agent or the grinding agent.
In order to solve the above mentioned technical problem, the present invention essentially provides in one aspect thereof a heater comprising a large diameter glass tube; a carbon wire heating element sealed in said large diameter glass tube and having opposite ends; a small diameter glass tube charged with compressed wire carbon members at opposite ends thereof, said compressed wire carbon members tightly holding said opposite ends of the carbon wire heating element therebetween; and a sealed terminal section having connection lines for power supply held between said carbon wire material, said connection lines and said carbon wire heating element being electrically connected to each other by way of said wire carbon members.
Also in order to solve the above mentioned technical problem, the present invention essentially provides in another aspect thereof, a heater comprising a carbon wire heating element having opposite ends; a small diameter glass tube charged with compressed wire carbon members at opposite ends thereof, said compressed wire carbon materials tightly holding said opposite ends of the carbon wire heating element therebetween such that said small diameter glass seals carbon wire heating element therein; and a sealed terminal section having connection lines for power supply held between said carbon wire material, said connection lines and said carbon wire heating element being electrically connected to each other by way of said wire carbon members.
In this connection, it is preferable that said large diameter glass tube and said small diameter glass tube are formed of quartz glass.
In order to solve the above mentioned technical problem, the present invention essentially provides in a further aspect thereof, a heater a plate-like glass member; a carbon wire heating element sealed in said plate-like glass member and having opposite ends; a small diameter glass tube section charged with compressed wire carbon members, said compressed wire carbon members tightly holding said opposite ends of the carbon wire heating elements therebetween; and a sealing terminal section having connection lines for power supply held between said carbon wire members, said connection lines and said carbon wire heating element being electrically connected to each other by way of said wire carbon members.
Thus, the present invention relating to the heater is characterized in that the connection lines are held in a compressed manner between the wire carbon members. Therefore, the carbon contents of the wire carbon performs a reducing reaction to prevent the connection lines from being oxidized with the result that any generation of sparks accompanying the oxidation of the connection lines.
Further, since the carbon wire heating elements and the connection lines are attached to the wire carbon members at their compressed portions, the connection are prevented from becoming loose due to the high temperature of the carbon wire heating element, thus assuring a good electrical connection.
Further, since the carbon wire heating element is used, a wet etching agent, a grinding agent or the like is prevented from metallic contamination spreading by way of the glass tube from the heating element.
It is preferable that said aid wire carbon members and said carbon wire heating element are held in a compressed state to extend substantially in parallel to an axis of said small diameter quartz glass tube section.
Further, it is preferable that each of said wire carbon members and said carbon wire heating element is prepared by binding a plurality of carbon fibers into a carbon fiber bundle and weaving a plurality of such carbon fiber bundles into a knitted cord or a braid.
In this way, since said wire carbon members and said carbon wire heating element are accommodated in parallel to the axis of the small diameter glass tube in a compressed state, the connection between said wire carbon members and said carbon wire heating element will not become loose, thus assuring a good electrical connection.
Particularly, said wire carbon members and said carbon wire heating element which are composed of knitted cords or braids woven from a plurality of fiber bundles each of which is prepared by binding carbon fibers have elasticity in the direction of the small diameter glass tube to assure a positive retention of the connection lines without the likelihood of becoming loose with the result that a good electrical connection is maintained.
It is preferable that said small diameter glass tube section accommodates one or more carbon wire heating elements therein and is charged with a plurality of wire carbon members and it is also preferable that said wire carbon members and said carbon wire heating elements are formed of an identical material to each other, the number of said wire carbon members is five times or more that of said carbon wire heating elements.
In this way, in the event the number of the wire carbon members are equal to or more than the number of the carbon wire elements, the heat from the wire carbon materials may be lowered.
Also, since the interposition of the wire carbon members between the carbon wire heating element and the connection lines minimizes the conduction of the heat from the carbon wire heating element, thus preventing the degradation of the sealing terminal section due to the high temperature.
Particularly, in the event that the number of the wire carbon members is five or more times the number of said carbon wire heating element, a remarkable effect results.
It is preferable that said sealing terminal section is composed of a glass tube including a glass portion, a graded seal portion, and a tungsten glass portion, said connection lines being pinch sealed at a pinch sealed portion, said glass portion being fused to said large diameter glass tube.
Since the glass tube constituting the sealing terminal section is thus composed, the structure of the sealing terminal section is simplified, the number of parts and man hours involved are reduced. Further, the glass tube to be integrate through fusion to a large diameter glass tube includes, taken from the glass the large diameter glass tube side, the glass portion, the graded seal portion and a tungsten glass portion, the damage thereto at a high temperature is prevented.
It is also preferable that said sealing terminal section is composed of internal connection lines electrically connected to said carbon wire heating element; external connection lines for power supply; a glass body formed with a plurality of grooves to receive said respective internal and external connection lines; conductive foils to electrically connect said internal and external connection lines; a glass tube to receive said internal and external connection lines such that said internal and external connection lines extend at one ends thereof out of said glass body, said glass body having an outer surface fusion connected to said glass tube; and a plug member to close one end of said glass tube, said glass body being fusion connected to a large diameter glass tube at the other end thereof.
Since the carbon wire heating element and the wire carbon members are thus accommodated in a compressed state, only insertion of the internal connection lines of the sealing terminal section into said compressed portion facilitates the connection of the carbon wire heating element and the sealing terminal section. Further, since a positive connection is assured, accidents due to sparks or short circuiting is prevented.
It is further preferred that said small diameter glass tube section integrally has a hairpin-shaped or spiral small diameter glass tube sealing said carbon wire heating element therein.
Since said small diameter glass tube is integrally has a hairpin-shaped or spiral small diameter glass tube such that the glass tube sealing the carbon wire heating element is provided in the form of a unitary tube member, the thermal capacity of the heating element sealing portion is lowered, thus obtaining a heater having a quick thermal response.
It is also preferable that said small diameter glass tube section and said small diameter glass tube are enclosed by said large diameter tube, and thus constructed, a heater having a remarkable mechanical strength and reliability is obtained.
It is also preferable that said small diameter glass tube charged with the compressed wire carbon members is provided integrally or separately beneath said solid glass body formed with grooves to receive said carbon wire heating element, said solid glass body receiving said carbon wire heating element at its outer surface thereof and said small diameter glass tube being enclosed by a large diameter glass tube, said solid glass body having an outer surface to be connected to said large diameter glass tube through fusion. Thus fusing the outer surface of the solid glass body to the large diameter glass tube, a heater of higher mechanical strength and reliability is obtained.
In this connection, the small diameter glass tube referred to in the invention stands for that having an inside diameter of at least about 5 to 15 mm (preferably 5 to 15 mm). In said small diameter glass tube, it is not preferable that the inside diameter of the portion where a plurality of wire carbon members are accommodated in a compressed state is less than 5 mm because the resultant coloric values are too large and it is also not preferable that with the diameter more than 15 mm because the heater can become too large.
Further, the thickness of the small diameter glass tube is about 1 to 2 mm (preferably 1 to 2 mm) and the large diameter glass tube referred to in the invention stands for a glass tube having an inside diameter larger than the sum of the outside diameters of at least two small diameter glass tubes; that is, a glass tube having the inside diameter exceeding 14 mm.
It is further preferable that said small or large diameter glass tube is composed of an elongated first flat glass plate formed with grooves to receive said carbon wire heating element therein and a second flat glass body to be fused to said first flat glass body to close said groove.
Thus, it is possible to form an elongated flat plate-like heating element by use of the elongated flat plate-like glass body such that a heater having a high mechanical strength and high reliability is obtained.
In this connection, the glass tube sealing the carbon wire heating element is not limited to an ordinary cylindrical tube but includes an elongated plate-like member with said elongated plate-like glass body fused.
It is also preferable that two separate glass tube constituting the sealing terminal section are provided, each including a glass portion, a graded seal portion and a tungsten glass portion in which the connection lines are sealed at the tungsten glass portion while said glass portion is fused to a small or large diameter glass tube to accommodate the carbon wire heating element. Thus constructed, it is possible to positively prevent a glow discharge between the connection lines.
It is also preferable that said glass body is formed by fusing a plurality of a flat or curved plate-like glass members into an integral member with at least one of said plate-like glass member being formed in one side thereof with grooves to accommodate said carbon wire heating element and the other side than said grooves being fused to the other plate-like glass member into an integral member. Thus integrally fused, a high mechanical strength is obtained.
In this way, the heater of the invention is suitable for directly dipping into a storage tank containing a wet etching agent or a grinding agent.
Particularly, the invention contributes to prevention of metallic contamination from the wet etching agent or the grinding agent and there is no likelihood of damage even if it is directly dipped into the storage tank containing the wet etching agent or the grinding agent to assure a high mechanical strength.
Further, the heater of the invention shows remarkable effects for prevention of metallic contamination in a heat treatments atmosphere in various heat treatment of semiconductors together with a high mechinical strength and long service life.